DISTRIBUTION AND SEASONAL MOVEMENTS OF SAGINAW BAY FISHES 



INTRODUCTION 



The reseaicb vessel Cisco, Bureau of Commer - 

 cial Fisheries, was used for experimental fishing in 

 Saginaw Bay and the adjacent waters of southern 

 Lake Huron in the summer and fall (June 3 -Novem- 

 ber 27) of 1956. Most fish were taken by trawls and 

 gill nets from depths greater than 10 feet, but collec- 

 tions were supplemented by samples from inshwe 

 seining at depths less than 3 feet. Distribution rec- 

 ords previous to this investigation were very scanty 

 for areas other than the shallow, inshore water of the 

 Bay. 



The collections of many species were too scat - 

 tered and infrequent to allow positive statements on 

 distribution and seasonal movement. Collections of 

 other species were sufficient, however, to provide 

 general infcsmation on local differences and season- 

 al changes of abundance. 



This paper is confined to fish caught in Saginaw 

 Bay, defined here as the water southwestward of a 

 line extending from Au Sable Point to Point aux 

 Barques (fig. 1). Another line from Point Lookout 

 (northwest shore) through Charity Island to Oak Point 

 (southeast shore) was chosen to divide the "inner bay" 

 from "outer bay. " The outer bay was further divided 

 into shallow (out to 7 1/2 fathoms) and deep (8-25 

 fathoms) areas. Conditions in the inner bay and shal- 

 low areas of the outer bay are similar to those com - 

 monly found in inland lakes, whereas conditions in 

 the deeper outer bay approach those of the open waters 

 of Lake Huron. 



Common names of fish are used throu^out the 

 text except for several species of the genus Coregonus 

 for which only specific names are used. Both com- 

 mon and scientific names are listed for each species 

 in tables 2 and 3. 



COLLECTION OF MATERIALS AND DATA 



Most trawling was carried out in daylight, but 

 some night trawling was conducted each cruise. The 

 trawling speed of the Cisco was approximately 3 m. p. h. 

 It varied slightly, depending upon the influence of 

 winds and currents. Trawls usually were towed for 10 

 minutes. Some tows were cut short because of obsta- 

 cles, and a few longer tows were made to determine 

 the variation of catch with time; the total time range 

 was 3 to 30 minutes. All trawling data recorded in 

 this paper were from tows made on the bottom along 

 the contour. Occasionally the tiawl did not operate 

 properly or was snagged and torn. Data from these 

 tows and from midwater tows were not included in the 

 quantitative records. Of the three types of trawls fished, 

 the most successhil and frequently used was trawl No. 

 2 (table 1). 



Experimental nylon gill nets were set on the bot - 

 torn at various depths and obliquely from the surface 

 to the bottom. The gangs of giU nets set on the bot- 

 tom included 250 feet each of 2 1/4-, 2 1/2 -, 2 3/4-, 

 3-, and 4 -inch mesh, extension measure; these nets 

 were 6 feet deep. During Cruise 9 (November 18-21), 

 100 feet of 2 -inch mesh and 50 feet each of 1 - and 

 1 1/2 -inch mesh were added to the original gang. At 

 Station 11 separate gangs of 2 1/2- and 3 1/2-inch 

 mesh were set obliquely at 13 fathoms (two 250 -foot 

 nets of each mesh). Nylon bull nets --2 1/2 -inch 

 mesh, 120 meshes deep, and 300 feet long --were set 

 on the bottom (November 19) and susi>ended 1 fath- 

 om below the surface (June 26). 



Seining was conducted at 10 inshore stations 

 (fig. 1). All seine hauls were made during daylight 

 with a 1/2 -inch -mesh seine (without bag) 30 feet 

 long and 3 feet deep. The hauls were from 50 to 300 

 feet per drag in water up to 3 feet deep. 



Most fish were identified in the field. The iden- 

 tity of questionable specimens was verified later in 

 the laboratory. At least one representative from each 

 species is preserved in the Bureau 's collection. 



Trawls, seines, and nylon gill nets (both shoal 

 gill nets and bull nets) were used for collecting fish. 

 Station locations, except for seining, were plotted 

 with the aid of radar, and water depth was recorded 



by an echo-sounder. \l 



y See Moffen (1954) for desaiption of Cisco 

 equipmeat. 



Distribution records in this survey are based up- 

 on 10 trawling, 6 gill netting, and 10 seining sta- 

 tions (fig. 1). Five locations were utilized as both 

 trawling and gill netting stations. Most trawling and 

 gill netting stations were visited periodically from 

 June through November (see appendix table 1). All 



